REVISION. OF THE DEEP-WATER MOLLUSCA OF THE ATLAN'fIC COAST OF NORTH AMERICA, WITH DE­ SCRIPTIONS OF NEW GENERA AND SPECIES. PART I.-BIVALVIA. By ADDISON E. VERRILL, P"ojessor oj Zoology in Ya.7e Uni"ersity 'and KA'l'HARINE J. BUSH, Assistant in Peabody Museum oj Yale Uni"erBity. THIS article is not intended as a review of all the known species found oft· our coasts. It is preliminary to a much more extensive report, in which full details of the distribution of all the species col­ lected will be given, and for which the detailed tables have beeu pre­ pared, giving every 8tation for each species, with its position, depth, temperature, character of t,he bottom, etc. Many of the larger and more prominent species were described and figured by the senior author several years ago in various papers pub· lished in the Transactions of the Connecticut Academy alld elsewhere. The smaller and more difficult species were put asille at that time, for more careful study. and are now presented. The families that are most fully treated in this article are the Ledidre, Cuspidaridre, Diplodontidre, amI Pectillidre. These include a very large number of deep-sea species in every region, and their species are often very difficult to distinguish without long and patient microscopic study and direct comparison of large series of specimens from various localities. _ The present article is intended to give some of the result·s of studies of this kind, made during several years, of the large series of speci­ mens dredged by the United States Fish Oommission off our coasts from] 871 to 1887, together with those previou8ly dredged by the senior author in the same region. PROCEEDINGS U. S: NATIONAL MUSEUM, VOL. XX-No. 1139. 775 776 PROOEEDINGS OF THE NATIONAL MUSEUM. VOL. Xx. In order to avoid, so far as possible, the uncertainty necessarily connected with lUere descriptions of these forms, we ha\'e had large camera-lucida figures made, as carefully as possible, not only of the new species, but also of some of those previously described from our coast, for comparisou. It is, therefore, to be hoped that future investi­ gators may at least be able to'understand the characters of the species now recognized by us, whether they agree witll our determinations or not. Although the collections studied are nnusually extensive, and the number of stations represented is very large, it is noteworthy that a considerable number of species were met with but once, and sometimes only a single specimen was obtained. This indicates that many addi­ tional species of snch small deep,sea shells would be disc(wered in the same region if additional dredgings should be made. Our investigations have enabled us to add to the fauna lIine genera, four subgenera, and about eighty species alld varieties, of which about seventy are described as new species and seven as new varieties; of tIlese, twelve species and one variety belong to the southern fanna. 'fhe following list shows the geuera in which the new species and varieties are inCJluded.! The lIew genera are printed in italic: ]{arte8iella, 1. Poromya, var. 1. Bathyarca, 2. Abra, var:1. Cetoconcha, 2. Bentharca. Macoma,1 Cetomya,1. Limopsis, 2. Montacuta, 4, var. 2. Lyonsiella, 2. Solemya,1. Kelliop8i8. Lyonsia,1. Nucula, 1, var. 1. Cr~'ptodon, 4, var. 1. Clidiophora, 1. Leda, 1. Axinulu8, 6. Kennerlia, 1. Ledella, 1, var. 1­ Axinopsis, 1, Val'. 1. Periplomn, 1. Adranella, 1­ Axinodon; 1. Limatula, 3. Microyoldia. LeptaxinU8, 1. Chlamys,2. Yoldiella, 11, var. 1. Cuspidaria, 8. Hyalopecten, 1. o Malletia, 2. Cardiomya, 2. Camptonectes, 1. 0 Neilonella, 1. Halonympha, 1. Cyclopecten, 2. Tindaria, 3. Myonera,3. No attempt has been made to give the complete synonymy and details of the distribution. Such matters have been reserved for the final report on the collections. Unless otherwise stated, the station numbers are those of the United States Fish Commission and the Berial numbers are those of the United Htates National Museum. The drawings, with few exceptions, were made by Mr. Alphens H. Verrill, under the immediate supervision of the authors. Peabody MU86Ullt of Yale UtliVer8ity, New HOiven, OontllJctiout, Januarg25, 1897. lOwing to the long delay in the publication of this article, some of the new species and geuera have been published elsewhere, so that these numbers are uot now strictly correct. 11'0.1139. DEEP·WATER MOLLUSCA-VERRILL Aim BUSH. 777 Family PHOLADID.A!1. MARTESIELLA, new subgenus. This subgeneric name is proposed for the following species, which difters from Martesia, iii having a well· defined, elongated, median, dorsal plate, posterior to the umbos, in addition to the shield-shaped one over them. MARTESIA (MARTESIELLA) FRAGILIS, new species. (Plate LXXIX, fig. 10.). Shell small, white, tbiu, fragile, wedge-shaped. The anterior end is very sbort and broadly rounded, the aperture I1t'arly closed in our largest specimen by a pair of callous plates. The antero·dorsal margin is recurved toward the umbos, but notappressed, and forms a deep, spiral, open cavity. The' valves have a very obtuse anterior emargination. A broad and moderately deep sulcus runs from the beak to the veutral mar~in; in front of tbis the surface is covered by thin concentric ribs, which curve downwal d at the sulcus and form a distinct angle in line with th~ anterior emargination and correi:lponding with a slight ridge on the surface; these cOlleentric ribs are crossed by fine radiating lines, which produce tine scrrations on their edges. Posterior to the sulcus the surface is marked ollly by irregular lines of growth, which, near it, take the form of more distinet grooves or ridges. The posterior end is prolonged, compres~ed, amI bluntly rounded. The umbonal plate is thick, relativel.\' largt', and nSl1ltlly heart-shaped, with the posterior end broader and distinctly emltrginate in the middle; the anterior enC\. tapers somewhat and is blunt and angulated, or sometimes subacute. '1'he posterior dorsal plate is long, narrow, and somewhat spatulate or clavate, anf! stands well in relief above the dorsal margin, with the edges free and the narrow anterior end running 'under the posterior end of the umbonal plate. Length of one of the largest specimens, 7 mm.; hejght, 4.5 mm.; thickness, 4 mm. Young specimens 3 or 4 mm. in length are relatively shorter and ttticker than the larger one~, but even these have the anterior callous pretty well developed; the nmbonal plate is usually shield-shaped, the lateral borders emarginate, in contact with the most prominent part of the umbos; the posterior border is distinctly emarghmte, ami the anterior end has a central point or mucro, sometimes defined by slightly concave posterior edges. - Many live specimens were found in a piece of' wood floating near station 2566, N. lat. 37° 2;1', W.long. 680 8/, 1l:)l:)5. 778 PROOEEDINGS OF THE NATIONAL MUSEUM. YOL.XL Family SEMELID.lE. ABRA LONGICALLIS (Scacchi), variety AMERICANA, new. (Plate LXXXIII, figs. 6,7.) Abra longicallis VERRILL, Trans. Conn. Acad., VI, pp. 224,278, 1884. Our specimens differ from the European form described and figured by G. O. Sal's I in having the posterior lateral tooth less remote and the cartilage-pit or chondrophore longer, the antero-dorsal margin more convex, and the whole Rhell relatively broader. A very few specimens were obtained at six stations between N. lat. 390 49', W. long. 680 28' 30", and N.lat. 360 16' 30", W.long. 68°,21', in 924 to 2,620 fathoms, 188;j~1886. Family TELLINID.lE. MACOMA INFLATA Dawson. (Plates LXXVII, fig. 1; LXXXVIII, fig. 6.) Maooma inflata (STIMPSON ~ISS.) DAWSON, C..nallian Naturalist, VI, p. 377, 1872.-VERRILL, 'PranR. Conn. Acatl., V, p. 568, 1882. A numher of live specimens and separ'ate valves were obtained at six stations between N: lat. 47°40', \V.long. 47°35' 30", and N.lat. 400 3', W. long. 70° 31', in 57 to 206 fathoms, 1877-1886. Murray Bay.- . Da.wsou. Gulf of St. Lawrence.-Coll. Whiteaves. Family PETRICOLIDJE. CHORISTODON? CANCELLATUS Verrill. (Plate XCVI, figs. 2, 3.) Choristodon r cancellatus VERRILL, Trans. Coun. Acad" VI, p. 435, 188.:;.-DALL, Bull. U. S. Nat. MllS., N... 37, p. 58, 1889. One valViol, station 2265, oft· Chesapeftke Bay,in 70 fathoms, 1884. Family KELLIELLIDJE. KELLIELLA NITIDA Verrill. (Plates XCI, fig. 8; XCIII, fig. 10.) Kelliella 8p. VERRILL, Trans. Conn. Acad., VI, p. 279, 1884; Expl. Albatro8s, Report U. S. Com. Fish and Fisheries for 1883, p. 576, 1885. KoWol/a nitida VERRILL, TrailS. COUll. Acad., vr, p. 438, 1885. Comparatively few specimens, at seven stations between N. lat. 390 5' 30", W. long. 70°44' :30", and N. lat. 38° 20', W. long. 700 8' 30", in 1,525 to 2,033 fathoms, lS83-1S86. I Mollusca Reg. Arcticre Norvegire, p. 74, pI. 6, figs, 3 a-o; pI. 20, fig, 4, 1878. NO. 1139. DEEP-WATER MOLLUSCA-VERRILL AND BUSH. 779 Family LEPTONID1E or ERYCINID1E. KELLIA SUBORBICULARIS (Montagu). (Plate XCIV, figs. 3, 4.) Kellia 81tborbiculari8 R. and A. ADAMS, Genera Recent Moll., II, p. 475; III, pl. CXIV, figs. 8 a-c, 1858.-.JEFFREY8, British Conchology, II, p. 225, pl. v, fig. 3, 1863; V, p. 179, pl. XXXII, fig. 2, 1869.-GOULD, Hep. on Invert. of Mass., Binney's ed., p. 83, fig. 394, 1870.-'rRYON, ArneI'. Mal'. Conch., p. 171, pI. 32, figs. 433, 435, 1873.-G. O. SAHS, Mollusca Reg. Arcticffi Nor\-egire, p. 67, pl. 19, figs. 14 a-b, 1878.-JEFFREYS, Proc. Zoo1. Soc., London, p. 7QO, June, 1881.-S!Il:ITH, E. A., Report Vo~'.